Coil spring forming apparatus and coil spring formed thereby

ABSTRACT

A coil spring forming apparatus including a core bar  2  which rotates around an axis thereof and on which a wire material W fed from a wire material-feeding means is wound; a clamping portion  22  which rotates integrally with the core bar  2  and grips an end of the wire material W on the core bar  2 ; and first guide rollers  30  and second guide rollers  40  for guiding the wire material W onto the core bar  2 ; wherein the first guide rollers  30  and the second guide rollers  40  are provided so as to move independently from each other in parallel with the axis of the core bar  2 , and a coil spring formed by the above coil spring forming apparatus.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/513,845, filed on May 6, 2009 as the U.S. National Phase under 35U.S.C. §371 of International Application PCT/JP2007/071301, filed Nov.1, 2007, which claims priority to Japanese Patent Application No.2006-300210, filed Nov. 6, 2006, which are hereby incorporated byreference in their entirety.

TECHNICAL FIELD

This invention relates to a coil spring forming apparatus and coilsprings. More specifically, the invention relates to a coil springforming apparatus capable of correctly forming coil springs of variouspitches and pitch angles and coil springs formed by the same coil springforming apparatus.

BACKGROUND ART

A known coil spring forming apparatus comprises, for example, a core barand a lead screw provided in parallel with the core bar. The lead screwof the coil spring forming apparatus has a spiral groove that is formedso as to correspond to a pitch and a pitch angle of a coil spring thatis to be formed. In the above coil spring forming apparatus, the corebar and the lead screw are rotated, the wire material is guided on thecore bar by the spiral groove of the lead screw, and the wire materialis wound round the core bar in a predetermined pitch and a pitch angleto manufacture a coil spring.

However, the above coil spring forming apparatus involves variousproblems such as requiring laborious work to design and fabricate thelead screw, lacking general applicability, i.e., being capable offorming only a coil spring having a pitch and a pitch anglecorresponding to the spiral groove of the lead screw, and it being verydifficult to produce coil springs having a pitch or a pitch anglechanging greatly at a midway point.

Consequently, a coil winding machine employing a pulley-like guide inplace of the above lead screw has been developed. The coil windingmachine has a core bar and a pulley-like guide arranged at a positionseparated away from the core bar in the radial direction thereof, andthe pulley-like guide moves along the axial direction of the core bar ata predetermined speed. The wire material is wound round the core barwhile being guided by the pulley-like guide. Here, the pitch and thepitch angle of the coil spring that is to be obtained is controlled bycontrolling the moving speed of the pulley-like guide.

In the above coil winding machine, however, the pulley-like guide isdisposed at a position separated away from the core bar, and the wirematerial is not directly guided onto the core bar. Therefore, whileestimating the pitch and the pitch angle of the wire material that isactually wound on the core bar, the motion of the pulley-like guide mustbe controlled in accordance with the estimated pitch and pitch angle.

Therefore, laborious work is required for preparing input data forcontrolling the pulley-like guide and, furthermore, the pitch of theobtained coil spring varies. Further, since the pulley-like guide andthe core bar are separated away from each other, it is not possible todirectly control the motion of the wire material on the core bar. Whenattempting to form a coil spring having a pitch that sharply varies,therefore, it is difficult to have the motion of the guide follow thechange in the pitch. When attempting to forcibly move the guide so as tofollow the change in the pitch, the wire material slips on the core bar,causing variation in the pitch.

In order to solve the problems of the above coil winding machine, therehas been proposed a coil winding machine comprising a core bar, a corebar drive mechanism, a chuck for gripping an end of a wire material soas to fix it on the core bar, a guide member arranged in parallel withthe core bar, a moving head being held by the guide member so as to movein a direction parallel with the core bar, a first holder being providedon the moving head so as to move reciprocally toward or away from thecore bar and to rotate around an axis which extends in the radialdirection of the core bar, a guide drive mechanism reciprocally drivingthe first holder toward or away from the core bar, a first guide beingprovided on the first holder and having a groove portion that fits thematerial of a coil spring, an axial drive mechanism driving the movinghead so that the first guide moves in the axial direction of the corebar in accordance with the pitch of the coil spring at a speedcorresponding to the rotational speed of the core bar, a second holderturning together with the first holder, a second guide being provided onthe second holder, coming in rotational contact with the material so asto prevent the material from detaching, and feeding the material towardthe first guide, and an angle-varying actuator controlling the directionof the holder to direct the first guide and the second guide so that thefirst guide and the second guide interlock and face a directioncorresponding to a pitch angle of the coil spring (patent document 1).

[Patent document 1] JP-B-2-33460

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In the above coil winding machine, after the end of the wire material isgripped by the chuck and fixed onto the core bar, winding of the wirematerial is started. As described above, however, the first guide isprovided on the first holder that approaches or separates away from thecore bar, and the second guide, which guides the wire material incooperation with the first guide, is provided on the second holder thatturns integrally with the first holder. At the start of winding the wirematerial, therefore, the first guide and the second guide must beretreated to a position that is separated away from the core bar.Accordingly, right after the start of winding the wire material, it isdifficult to correctly control the shape of the coil spring.

Additionally, the first holder and the second holder are only capable torotate integrally with each other around the axis extending in theradial direction of the core bar, and thus, positional relationshipbetween the first guide and the second guide is limited. Consequently,limitation is inevitably imposed on the pitch and on the pitch angle ofthe coil spring to be produced.

The present invention was achieved in order to solve the above problemsand has an object of providing a coil spring forming apparatus capableof correctly producing coil springs having various pitches and pitchangles.

Means for Solving the Problem

According to a first aspect of the invention, there is provided a coilspring forming apparatus comprising:

a core bar rotating around an axis thereof and on which a wire materialfed from a wire material-feeding means is wound;

a clamping portion rotating integrally with the core bar and grips anend of the wire material on the core bar; and

a first guide member and a second guide member guiding the wire materialonto the core bar;

wherein the first guide member and the second guide member are providedso as to move independently from each other in parallel with the axis ofthe core bar.

In the above coil spring forming apparatus, the wire material fed fromthe wire material-feeding means is guided by the second guide member andthe first guide member toward a position where the winding starts on thecore bar. An end portion of the wire material is fixed onto the core barby the clamping portion.

After the end of the wire material is fixed onto the core bar, the corebar rotates in a direction in which a coil spring is wound and, at thesame time, the first guide member and the second guide member move inparallel with the axis of the core bar to guide the wire material so asto be wound on the core bar maintaining a predetermined pitch and apredetermined pitch angle.

In the coil spring forming apparatus, the first guide member and thesecond guide member are moved at an equal and constant speed to form thecoil spring of a predetermined pitch and a pitch angle. Further, whilemoving the first and the second guide members at an equal speed, byincreasing the speed thereof, the pitch and the pitch angle can beincreased in the direction in which the first guide member and thesecond guide member move. Conversely, while moving the first and thesecond guide members at an equal speed, by decreasing the speed thereof,the pitch and the pitch angle can be decreased in the direction whichthe first guide member and the second guide member move.

Further, by moving the second guide member at a speed higher than thefirst guide member while moving the first guide member at apredetermined speed, the wire material is bent with the first guidemember as a center, and the wire material is wound at a larger pitch anda larger pitch angle in a portion downstream of the bending portion ofthe wire material in the direction in which the first guide member andthe second guide member move. Conversely, by moving the second guidemember at a speed lower than the first guide member while moving thefirst guide member at a predetermined speed, the wire material is woundat a smaller pitch and a smaller pitch angle in a portion downstream ofthe bending portion in the direction in which the first and the secondguide members move.

By setting the moving speeds of the first guide member and the secondguide member in the coil spring forming apparatus as described above, itis made possible to form not only a coil spring having a constant pitchbut also a coil spring having a pitch increases or decreases in theaxial direction thereof, and coil springs having larger or smaller pitchand pitch angle in a portion downstream from a predetermined point.

According to a second aspect of the invention, there is provided thecoil spring forming apparatus of the first aspect, wherein, of the firstguide member and the second guide member, the first guide memberdisposed on the side closer to the core bar holds a portion of the wirematerial adjacent to the portion of the wire material clamped by theclamping portion on the core bar at the start of winding of the wirematerial.

In the above coil spring forming apparatus, the first guide member holdsa position of the wire material that is offset toward the side close tothe wire material-feeding means from the position of starting thewinding at the start of winding. Therefore, the wire material is guidedby the first guide member and the second guide member along apredetermined passage from the start of winding, and thus, the pitch andthe pitch angle of the coil spring can be correctly controlled even atthe start of winding. Consequently, it is made possible to correctlyform a coil spring having flat seats at both ends thereof like asuspension coil spring for automobiles.

According to a third aspect of the invention, there is provided the coilspring forming apparatus of the first or second aspect, wherein thefirst guide member and the second guide member are each provided with apair of guide rollers arranged so as to sandwich the wire materialpassage therebetween, the guide rollers of the first guide member comein contact with the wire material from the upper side, and the guiderollers of the second guide member come in contact with the wirematerial from the lower side.

In the above coil spring forming apparatus, the first guide member andthe second guide member are each provided with the pair of guide rollersarranged so as to hold the wire material passage therebetween.Therefore, both the first and the second guide members are capable ofsmoothly feeding the wire material regardless of their angles relativeto the wire material. Further, since the first guide member located onthe side close to the core bar pushes the wire material from the upperside, the coil spring can be formed more constantly.

According to a fourth aspect of the invention, there is provided thecoil spring forming apparatus of the first or second aspect, wherein thesecond guide member comprises a pair of guide rollers that are arrangedso as to sandwich the wire material passage therebetween, and the firstguide member comprises a guide roller having a groove that fits the wirematerial and a guide roller support member supporting the guide rollerso as to rotate around the axis of the guide roller, the guide rollersupport member being rotatable around an axis which is at a right anglewith the axis of the guide roller and at a right angle with the wirematerial feed passage.

In the above coil spring forming apparatus, the wire material can besmoothly delivered regardless of the angle between the second guidemember and the wire material, and thus, the wire material is not bent atthe second guide member even when the first guide member and the secondguide member are driven at different speeds. In the above coilapparatus, further, if the first guide member and the second guidemember are driven at different speeds, the wire material is bent at theposition of the first guide member and in this case, a force urging thewire material to get out of the groove of the guide roller acts betweenthe wire material and the guide roller. However, in the first guidemember, the guide roller support member rotates around the rotary axisso that the direction of the groove of the guide roller coincides withthe direction of the wire material that has been bent. Therefore, it ispresented from happen that the wire material gets out of the guideroller by the above-mentioned force, and that the wire material isrubbed so strongly onto the groove of the guide roller that the guideroller is damaged.

According to a fifth aspect of the invention, there is provided a coilspring formed by the coil spring forming apparatus of any one of thefirst to fourth aspects.

Effect of the Invention

As described above, the present invention provides the coil springforming apparatus capable of correctly producing coil springs havingvarious pitches and pitch angles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the whole constitution of a coilwinding machine according to an embodiment 1.

FIG. 2 is a front view showing the whole constitution of the coilwinding machine according to the embodiment 1.

FIG. 3 is a schematic view showing the constitution of a first guideroller, a second guide roller, a core bar and peripheries thereof in thecoil winding machine according to the embodiment 1.

FIG. 4 is a sectional view showing, on an enlarged scale, theconstitution of the first guide roller and the peripheries thereof inthe coil winding machine of FIG. 1.

FIG. 5 is an enlarged side view showing the constitution of the firstguide roller and the peripheries thereof in the coil winding machine ofFIG. 1.

FIG. 6 is an enlarged top view showing the constitution of the firstguide roller and the peripheries thereof in the coil winding machine ofFIG. 1.

FIG. 7A is a view illustrating the motions of the first guide roller andthe second guide roller at the start of winding by feeding a wirematerial to a core bar in the coil winding machine of FIG. 1.

FIG. 7B is a view illustrating the motions of the first guide roller andthe second guide roller when the wire material is wound on the core barat a pitch angle θ1 in the coil winding machine of FIG. 1.

FIG. 8A is a view illustrating the motions of the first guide roller andthe second guide roller just before changing the pitch angle from θ1 toθ2 in the coil winding machine of FIG. 1.

FIG. 8B is a view illustrating the motions of the first guide roller andthe second guide roller when the pitch angle is being changed from θ1 toθ2 in the coil winding machine of FIG. 1.

FIG. 9A is a view illustrating the motions of the first guide roller andthe second guide roller at the time of forming flat seats at the ends ofa coil spring in the coil winding machine of FIG. 1.

FIG. 9B is a view illustrating the motions of the first guide roller andthe second guide roller when the wire material is to be wound on thecore bar at the pitch angle θ1 after the flat seats have been formed atthe ends of the coil spring in the coil winding machine of FIG. 1.

FIG. 10 is a side view illustrating a coil spring having flat seats atboth ends thereof.

FIG. 11 is a diagram illustrating relationships between the pitch of thecoil spring and the number of turns of the wire material when the pitchangle is increased from θ1 to θ2 and is returned again to θ1 on the wayof forming the coil spring by using the coil winding machine of theembodiment 1 and a conventional coil winding machine.

FIG. 12 is a perspective view showing the whole constitution of the coilwinding machine according to an embodiment 2.

FIG. 13 is a schematic view showing the constitution of a first guideroller, a second guide roller, a core bar and peripheries thereof in thecoil winding machine according to the embodiment 2.

FIG. 14 is a view showing, on an enlarged scale, the constitution of thefirst guide roller and the peripheries thereof in the coil windingmachine of FIG. 12.

FIG. 15 is a view showing, on an enlarged scale, the constitution of thesecond guide roller and the peripheries thereof in the coil windingmachine of FIG. 12.

FIG. 16A is a view illustrating the motions of the first guide rollerand the second guide roller at the start of winding by feeding the wirematerial to the core bar in the coil winding machine of FIG. 12.

FIG. 16B is a view illustrating the motions of the first guide rollerand the second guide roller at the start of winding the wire material onthe core bar at the pitch angle θ1 in the coil winding machine of FIG.12.

BEST MODE FOR CARRYING OUT THE INVENTION 1. Embodiment 1

A coil winding machine which is an example of the coil spring formingapparatus of the invention will be now described below.

As shown in FIGS. 1 and 2, the coil winding machine 1 according to theembodiment 1 includes a cylindrical core bar 2 on which a wire materialW will be wound, and a first guide portion 3 and a second guide portion4 for guiding the wire material W fed from feeding means (not shown)toward the core bar 2.

The first guide portion 3 and the second guide portion 4 are driven inparallel with the axis of the core bar 2 by, a ball screw mechanism 5and a ball screw mechanism 6. The ball screw mechanism 5 and the ballscrew mechanism 6 are provided on a plate-like board 9 disposed inparallel with the core bar 2. A guide rail 7 is provided at a lower edgeportion on the surface of the board 9 on which the ball screw mechanism5 and the ball screw mechanism 6 are provided in parallel with the corebar 2, and a guide rail 8 is provided near the upper edge portion on theabove surface. Lower edge portions of the first guide portion 3 and thesecond guide portion 4 slidably engage with the guide rail 7, and upperedge portions of the first guide portion 3 and the second guide portion4 slidably engage with the guide rail 8. Therefore, the first guideportion 3 and the second guide portion 4 move on a plane in parallelwith the board 9.

Each of the portions of the coil winding machine 1 will be describedbelow in detail.

As shown in FIGS. 1 to 3, the core bar 2 has a flange portion 20 formedat its one end protruding outward in the radial direction thereof and amotor 24 attached to the other end thereof. By the motor 24, the corebar 2 rotates around the axis thereof in a direction in which the wirematerial W is wound. A clamping portion 22 is provided at one end of thecore bar 2 to come in contact with, and separate away from, the core bar2 and to rotate together with the core bar 2 adjacent to the flangeportion. As the clamping portion 22 approaches the core bar 2, the wirematerial W is gripped on the core bar 2.

As shown in FIGS. 1 to 4, the first guide portion 3 includes a pair offirst guide rollers 30 that rotate in contact with the wire material W,a support plate 32 supporting the first guide rollers 30 by shafts, abase plate 34 whose upper and lower ends are supported and guided by theball screw mechanism 5, by the guide rail 7 and by the guide rail 8, andan arm member 36 supported, at its one end, by the base plate 34 andsupports, at the other end, the support plate 32 so as to rotate arounda vertical rotary axis.

As shown in FIGS. 1 and 2, the base plate 34 has a block. 34A fixedthereto to travel on the guide rail 7 and a block 34B fixed thereto totravel on the guide rail 8. The base plate 34 is guided by the block 34Aand the block 34B along the guide rail 7 and the guide rail 8.

The first guide rollers 30 correspond to the first guide member of theinvention and, as shown in FIGS. 2 to 6, have cylindrical side surfacesand are supported by the support plate 32 through rotary shafts 31. Therotary shafts 31 are arranged in an inverted V-shape as viewed from theside surfaces thereof and, therefore, the first guide rollers 30 arearranged in a V-shape as viewed from the side surfaces thereof.Therefore, the first guide rollers 30 are arranged so as to hold thepassage of the wire material W from both sides thereof and, at the sametime, come in contact with the surfaces of the upper side of the wirematerial W or, in other words, come in contact with the surfaces of theside opposite to the side that comes in contact with the core bar 2.Further, as shown in FIGS. 3 and 7A, by the support plate 32, the armmember 36, and the base plate 34, the first guide rollers 30 are drivenin parallel with the axis of the core bar 2 in a state of beingsupported at a position close to the winding start position and on theside of the wire material-feeding means as viewed from the end surfaceof the core bar 2, or in other words, at a position offset toward theside of the second guide portion 4.

Referring to FIGS. 1 and 2, the arm member 36 is supported by the ballscrew mechanism 35 that is provided on the base plate 34 so as to moveup and down. The ball screw mechanism 35 is constituted of a ball screw35A supported by the base plate 34, a nut portion 35B that is fixed tothe arm member 36 and engages with the ball screw 35A, and a motor 35Cthat rotates the ball screw 35A. As the motor 35C rotates, the nutportion 35B moves up and down to set the height of the arm member 36 andthe height of the support plate 32, and accordingly, the height of thefirst guide rollers 30 is also set.

Referring to FIGS. 1 to 3, the second guide portion 4 includes a pair ofsecond guide rollers 40 that are supported so as to rotate about a pairof rotary shafts 41, a plate-like support plate 42 supporting the secondguide rollers 40 rotatably, a base plate 44 whose upper and lower endsare supported and guided by the ball screw mechanism 6, by the guiderail 7 and by the guide rail 8, and an arm member 46 horizontallysupported at the root portion thereof by the base plate 44 and supportsat the end portion thereof the support plate 42 in parallel with avertical plane.

The base plate 44 has a block 44A fixed thereto to travel on the guiderail 7 and a block 44B fixed thereto to travel on the guide rail 8. Thebase plate 44 is guided by the block 44A and the block 44B along theguide rail 7 and the guide rail 8.

The second guide rollers 40 correspond to the second guide member of thepresent invention and, as shown in FIGS. 1 to 3, have cylindrical sidesurfaces and are supported by the support plate 42 through rotary shafts41. The second guide rollers 40, rotary shafts 41 and roller supportplate 42 assume the arrangement that is turned upside down thearrangement of the first guide rollers 30, rotary shafts 31 and supportplate 32 in the first guide portion 3 shown in FIGS. 4 to 6.Accordingly, since the rotary shafts 31 are arranged in the V-shape asviewed from the side surfaces thereof, the second guide rollers 40 arearranged in the inverted V-shape as viewed from the side surfacesthereof. Therefore, the second guide rollers 40 are arranged so as tohold the passage of the wire material W from both sides thereof and, atthe same time, come in contact with the surfaces on the lower side ofthe wire material W or, in other words, come in contact with thesurfaces on the side that comes in contact with the core bar 2. Further,as shown in FIGS. 3, 7A and 7B, by the support plate 42, the arm member46 and the base plate 44, the second guide rollers 40 are arranged at aposition closer to the wire material-feeding means than the first guiderollers 30, or in other words, at a position separated away from thecore bar, and driven in parallel with the axis of the core bar 2.

Referring to FIGS. 1 and 2, the arm member 46 is supported by the ballscrew mechanism 45 provided on the base plate 44 so as to move up anddown. The ball screw mechanism 45 is constituted by a ball screw 45Asupported by the base plate 44, a nut portion 45B that is fixed to thearm member 46 and engages with the ball screw 45A, and a motor 45C thatrotates the ball screw 45A. As the motor 45C rotates, the nut portion45B moves up and down so as to set the height of the arm member 46 andthe height of the support plate 42, and accordingly, the height of thefirst guide rollers 40 also is set.

Referring to FIGS. 1 and 2, the ball screw mechanism 5 includes a ballscrew 50 that is supported at its both ends in parallel with the board 9and horizontally, a nut portion 52 that engages with the ball screw 50and is secured to an upper portion of the base plate 34 of the firstguide portion 3, and a motor 54 for rotating the ball screw 50.

Similarly, referring to FIGS. 1 and 2, the ball screw mechanism 6includes a ball screw 60 that is supported at its both ends in parallelwith the board 9 and horizontally, a nut portion 62 that engages withthe ball screw 60 and is secured to an upper portion of the base plate44 of the second guide portion 4, and a motor 64 for rotating the ballscrew 60.

The function of the coil winding machine 1 will be described below.

Prior to starting the winding, the first guide portion 3 and the secondguide portion 4 move to the winding start positions by the ball screwmechanism 5 and the ball screw mechanism 6. Therefore, as shown in FIG.7A, the first guide rollers 30 and the second guide rollers 40 are heldat positions adjacent to the flange portion 20 of the core bar 2.

The wire material W that is fed by the feeding means is guided by thefirst guide rollers 30, second guide rollers 40 and flange portion 20 ina direction at right angles with the axis of the core bar 2, andintroduced into between the core bar 2 and the clamping portion 22.

After the wire material W that is introduced between the core bar 2 andthe clamping portion 22, the wire material W is gripped at the windingstart position by the clamping portion 22 and the core bar 2. The corebar 2 is then rotated in a direction in which the coil spring is woundas indicated by an arrow ‘a’. At the same time, the first guide portion3 and the second guide portion 4 are driven at a predetermined speedtoward the other end of the core bar 2, i.e., toward the end on the sidewhere the motor 24 is provided as indicated by arrows ‘b’ and ‘c’.Accordingly as shown in FIGS. 7B and 8A, the wire material is spirallywound on the surface of the core bar 2 while maintaining a predeterminedpitch angle θ1, and a coil spring is thus formed.

To increase the pitch angle from θ1 to θ2 on the way as shown in FIG.8B, the moving speed vc of the second guide portion 4 is increased atfirst. Consequently, the wire material W is bent in a direction of anarrow ‘c’ with the first guide rollers 30 of the first guide member 3 asa center. After the wire material W is bent and the pitch angle hasincreased to θ2, the moving speed vb of the first guide portion 3 isincreased toward a moving speed equal to the moving speed vc of thesecond guide portion 4, and the wire material W is continuously wound.

In addition, referring to FIG. 10, to form a coil spring having flatseats at both ends, the wire material W may be wound in a manner asdescribed below. First, as shown in FIG. 9A, the core bar 2 is rotatedin a state where the first guide portion 3 and the second guide portion4 are standing at a position that is adjacent to the flange portion 20of the core bar 2, and the wire material W is wound along the flangeportion 20. A flat seat is thus formed. After the flat seat is formed,as shown in FIG. 93, the second guide portion 4 is moved firstly, andthe wire material W is bent until the pitch angle θ1 is attained. Afterthe wire material W is bent, the first guide portion 3 is moved at aspeed equal to that of the second guide portion 4. After the wirematerial W is wound in a predetermined number of turns on the core bar2, the second guide portion 4 stops firstly, and then the first guideportion 3 stops at a time when the pitch angle of the wire materialwound on the core bar 2 has become 0.

In the coil winding machine 1 of the embodiment 1, the ball screwmechanism 5 and the ball screw mechanism 6 are driven and stopped so asto independently control the moving speed of the first guide rollers 30in the first guide portion 3 and of the second guide rollers 40 in thesecond guide portion 4. Further, the first guide rollers 30 hold thewire material. W at a position offset from the winding start position ofthe clamping portion 22, and thus, the pitch and the pitch angle of thewire material W can be controlled from the start of winding.

Therefore, flat seats can be easily formed at both ends of the coilspring. Further, as shown in FIGS. 9A and 9B, the coil spring can bewound at the predetermined pitch angle θ1 immediately from the flatseat. Accordingly, a coil spring having an even spring characteristics,not allowing a wire material to be rubbed when contracted, andaccordingly, not allowing a coating on the surface to be peeled odd and,hence, maintaining a strong resistance against the corrosion can beobtained.

Additionally, as represented by a solid line in FIG. 11, when the pitchangle is increased from θ1 to θ2 and when the pitch angle is againturned to θ1 on the way of winding a coil spring, the pitch angle of thecoil spring can be correctly controlled. On the other hand, asrepresented by a broken line or a two-dot chain line in FIG. 11, whenforming the coil spring by a conventional coil winding machine, ashifting portion where the pitch angle shifts from θ1 to θ2 and from θ2to θ1 is necessarily provided at portions of the coil spring where thepitch changes.

In the first guide portion 3, further, since the wire material W ispushed by the pair of guide rollers 30 from the upper side and in thesecond guide portion 4, the wire material. W is pushed by the pair ofguide rollers 40 from the lower side, the wire material W can besmoothly fed.

2. Embodiment 2

Another embodiment of the coil winding machine included in the coilspring forming apparatus of the present invention described below.Hereinafter, the reference numerals same as those of FIG. 1 to FIGS. 9Aand 9B denote the same elements as those shown in these drawings.

Referring to FIG. 12, the coil winding machine 10 according to theembodiment 2 includes the cylindrical core bar 2 on which the wirematerial W is to be wound, and the first guide portion 3 and the secondguide portion 4 for guiding the wire material W fed from the feedingmeans (not shown) toward the core bar 2.

As shown in FIGS. 12, 13 and 14, the first guide portion 3 includes afirst guide roller 130 that rotates in contact with the wire material W,the support plate 32 supporting the first guide rollers 130 so as torotate about a horizontal rotary shaft 131, the base plate 34 whoseupper and lower ends are supported and guided by the ball screwmechanism 5, by the guide rail 7 and by the guide rail 8, and the armmember 36 supported, at its one end, by the base plate 34 and supports,at the other end, the support plate 32 so as to rotate about a verticalrotary shaft.

The first guide roller 130 corresponds to the first guide member of theinvention and, as shown in FIG. 14, is formed like a pulley with itsside surface being recessed in an arcuate shape, and comes in contactwith the wire material W at the arcuately recessed side surface thereof.Further, as shown in FIGS. 13 and 16A, by the support plate 32, the armmember 36 and the base plate 34, the first guide roller 130 moves inparallel with the axis of the core bar 2 in a state of being supportedon the side of the wire material-feeding means close to the windingstart position as viewed from the end surface of the core bar 2, or inother words, at a position offset toward the side of the second guideportion 4.

Referring to FIG. 12, the arm member 36 is supported by the base plate34 via a height-adjusting member 37. The height-adjusting member 35 isconstituted so as to move up and down relative to the base plate 34 by aheight-adjusting screw (not shown). By moving the height-adjustingmember 37 up and down, the heights of the arm member 36 and the supportplate 32 can be set, and accordingly, the height of the first guideroller 130 can also be set.

Referring to FIGS. 12, 13 and 15, the second guide portion 4 includes apair of second guide rollers 140 that are supported so as to rotateabout a pair of rotary shafts 141, the plate-like support plate 42supporting the pair of rotary shafts 141 in the form of an invertedV-shape as viewed from the front, the base plate 44 whose upper andlower ends are supported and guided by the ball screw mechanism 6, guiderail 7 and guide rail 8, and the arm member 46 horizontally supported,at its root portion, by the base plate 44 and supports, at an endthereof, the support plate 42 in parallel with the vertical plane.

As shown in FIG. 15, the second guide rollers 140 have a cylindricalside surface. As described above, the two second guide rollers 140 aresupported by the rotary shafts 141 in a manner that the space is widenedupward. Therefore, the second guide rollers 140 are arranged so as tohold the passage of the wire material W from both sides thereof and, atthe same time, come in contact with the surfaces on the upper side ofthe wire material W, or in other words, come in contact with thesurfaces on the side opposite to the side that comes in contact with thecore bar 2.

Referring to FIG. 12, the arm member 46 is mounted on theheight-adjusting member 47 by a screw 45B, and the height-adjustingmember 47 is mounted on the base plate 44 by a height-adjusting screw47A so as to move up and down. Further, an elongated hole is opened inthe root portion of the arm member 46 in the horizontal direction sothat the screw 47B is inserted therein. The second guide rollers 140 canbe set for their height by moving the height-adjusting member 47 up anddown relative to the base plate 44 by using the height-adjusting screw47A and can be set for their position in the horizontal direction bymoving the arm member 46 in the horizontal direction with the screw 47Bbeing loosed. The second guide rollers 140 are held at a positionseparated farther than the first guide roller 130 in the first guideportion 3 from the core bar 2.

Except the above-mentioned respects, the coil winding machine 10 has thesame constitution as that of the coil winding machine 1 of theembodiment 1.

The function of the coil winding machine 10 will be described below.

Prior to starting the winding, the first guide portion 3 and the secondguide portion 4 is moved to the winding start positions by the ballscrew mechanism 5 and the ball screw mechanism 6. Therefore, as shown inFIG. 16A, the first guide rollers 130 and the second guide rollers 140are held at positions adjacent to the flange portion 20 of the core bar2.

The wire material W fed by the feeding means is guided by the firstguide rollers 130, second guide rollers 140 and flange portion 20 in adirection perpendicular to the axis of the core bar 2, and is introducedbetween the core bar 2 and the clamping portion 22.

The wire material W introduced between the core bar 2 and the clampingportion 22, is, thereafter, gripped at the winding start position by theclamping portion 22 and the core bar 2. The core bar 2 is then rotatedin a direction in which the coil spring is wound as indicated by anarrow ‘a’. At the same time, the first guide portion 3 and the secondguide portion 4 are driven at a predetermined speed toward the other endof the core bar 2, i.e., the end on the side where the motor 24 isprovided as indicated by arrows ‘b’ and ‘c’. Accordingly, as shown inFIG. 16B, the wire material is spirally wound on the surface of the corebar 2 while maintaining a predetermined pitch angle θ1, and a coilspring is thus formed.

DESCRIPTION OF REFERENCE NUMERALS

-   1—coil winding machine-   2—core bar-   3—first guide portion-   4—second guide portion-   5—ball screw mechanism-   6—ball screw mechanism-   7—guide rail-   8—guide rail-   9—board-   10—coil winding machine-   20—flange portion-   22—clamping portion-   24—motor-   30—first guide roller-   32—roller support portion-   34—base plate-   35—height-adjusting member-   36—arm member-   40—second guide roller-   41—rotary shaft-   42—support plate-   44—base plate-   45—ball screw mechanism-   45A—ball screw-   45B—nut portion-   45C—motor-   46—arm member-   47—height-adjusting member-   50—ball screw-   52—nut portion-   54—motor-   60—ball screw-   62—nut portion-   64—motor-   130—first guide roller-   140—second guide roller

1. A coil spring comprising: a first pitch angle θ1; a second pitchangle θ2; wherein the coil contains substantially no shifting portionwhere the pitch angle changes from θ1 to θ2 or from θ2 to θ1.
 2. Thecoil spring according to claim 1, wherein the pitch angles are changed aplurality of times.
 3. The coil spring according to claim 1, wherein oneof the pitch angles is
 0. 4. The coil spring according to claim 1,wherein said spring is formed by apparatus comprising: a cylindricallyshaped core bar rotating around an axis thereof; a clamping portionprovided at an end of the core bar and which rotates integrally with thecore bar; and a first guide portion and a second guide portionconfigured to be able to move independently from each other in adirection parallel with the axis of the core bar.
 5. A method ofmanufacturing the coil spring according to claim 1, comprising: feedinga wire material between a core bar and a clamping portion through afirst guide portion and a second guide portion; gripping the wirematerial on the core bar with the clamping portion which rotatesintegrally with the core bar; rotating the core bar as the first guideportion and the second guide portion are moving at a predetermined speedtoward the other end of core bar so as to maintain the first pitch angleθ1; changing the speed of the second guide portion so that the pitchangle is changed from first pitch angle θ1 to the second pitch angle θ2;and changing the speed of the first guide portion so as to become thesame speed with the second guide portion.
 6. A method of manufacturing acoil spring according to claim 3, comprising: feeding a wire materialbetween a core bar and a clamping portion through a first guide portionand a second guide portion, wherein the first guide portion and thesecond guide portion are standing at a position that is adjacent to aflange portion of the core bar; gripping the wire material on the corebar with the clamping portion which rotates integrally with the corebar; rotating the core bar without moving the first guide portion andthe second guide portion so as to maintain the first pitch angle θ1 tobe 0; moving the second guide portion so that the pitch angle is changedfrom the first pitch angle θ1 to the second pitch angle θ2; and movingthe first guide portion in the same speed with the second guide portion.7. The method of manufacturing a coil spring according to claim 6,further comprising: stopping the second guide portion after the wirematerial is wound in a predetermined number of turns on the core bar;and stopping the first guide portion when the pitch angle becomes 0.